1. Field of the Invention
The present invention relates to an organic solvent-based ink for use in an ink-jet printer.
2. Prior Art
Several systems have been proposed for ink-jet recording; electric field controlled jet that is ejected under an electrostatic attractive force; drop-on-demand ink (impulse jet) that is ejected under the oscillating pressure created by a piezoelectric transducer; and thermal ink jet that is ejected under the pressure created by air bubbles formed and grown with heat. These and other known methods of ink-jet recording are capable of producing an image with a very high degree of resolution.
Inks used in ink-jet printer are generally of two types: water-based inks which employ water as the principal solvent, and organic solvent-based inks which employ organic solvents as the principal solvent. Images printed with water-based inks are usually low in water resistance whereas organic solvent-based inks are capable of providing printed image with improved water resistance and the prints produced have excellent quality.
Whichever type of inks are used in ink-jet printer, abnormal ink ejection frequently occurs for various reasons such as nozzle clogging, filter clogging and time-dependent changes in ink properties. Since this has been a major cause of limited application of ink-jet recording systems, it is very important to develop inks, particularly organic solvent-based inks for ink-jet printer, that can be ejected in a more consistent way and many proposals have been put forth to meet this need. For example, with a view to stabilizing the dissolution or dispersion of coloring materials used in inks, Japanese Patent Publication No. 344/1982 and Japanese Patent Application (OPI) Nos. 78050/1980, 3871/1982, 3873/1982 and 36381/1986 (a term "OPI" herein means unexamined Japanese Patent Publication) have proposed improvements centering on the solvents to be incorporated in organic solvent-based inks. However, the experiments conducted by the present inventors have shown that these prior art organic solvent-based inks cannot always be ejected in a consistent way.